Pin seam fabrics for use on papermaking machines are composed of a woven base fabric and the ends of the base fabric are provided with interdigitated loops that are connected by a removable pin. The base fabric can either be woven in endless form as disclosed in U.S. Pat. No. 3,815,645 or alternately, can be woven in flat form in which case loops are subsequently attached to the free ends of the fabric in a manner such as disclosed in U.S. Pat. Nos. 4,123,022 and 4,401,137.
U.S. Pat. No. 4,601,785 discloses a pin seam base fabric having a fibrous batt needled onto the base and which can be used as a felt in the press section of a papermaking machine. With the felt as produced by the aforementioned patent, the fibrous batt is needled onto a face of the base fabic while the base fabric is in endless form and the needled batt extends across the pin seam joint. To open the felt fo installation on a papermaking machine, the batt is slit at a location spaced from the pin seam joint, and the portion of the batt extending between the slit and the joint is pulled away or separated from the base fabric to provide to batt flap. The pin is then removed from the pin seam joint and the felt is opened to a flat condition so that it can be installed on the papermaking machine. After installation, the pin is reinserted within the interdigitated loops and the batt flap is secured to the base fabric either by adhesives or needling.
The construction in U.S. Pat. No. 4,601,785 has a distinct drawback in that the flap can be easily torn away from the remainder of the needled batt as it is separated from the base fabric due to the fact that the flap is only attached to the remainder of the batt by its own relatively short fibers. If the flap is torn away, it is difficult, if not impossible, to reapply the flap to the base fabric after installation of the felt on the papermaking machine and yet maintain a uniform density of the felt in the area of a reapplied flap as compared to the remainder of the felt. A nonuniform density can adversely effect the water extraction characteristics of the felt. The re-attached flap also has a tendency to tear away during operation on the papermaking machine.